THE BIOLOGY OF THE MUD-DAUBING WASPS 45 



Parasites and Usees 



One third of the cells, or to be exact 1,524 contained the 

 parasites Melittobia or evidences of their having been there. 

 This parasite was very destructive and was instrumental in 

 wiping out entire families in many instances. Of the 643 nests 

 only 210 were entirely exempt from their attacks, and the 

 smaller nests of 1 to 5 cells were the ones most favored in this 

 exemption. Of the 210 which were quite free from these para- 

 sites, 143 or 68 per cent, of them were nests of 1 to 5 cells, while 

 in the entire collection a scant 50 per cent, of the nests were of 

 that size. 



In this material we found that the common museum pest, 

 Anthrenus scrophulariae, ate not only the dried food as is its 

 custom, but larva and spiders as well. In some cases we found 

 them in the open cells wherefrom the adults had emerged, 

 feeding upon the remains of the pupal case and fragments of 

 spiders' legs, but these were not counted; only those were con- 

 sidered which were found alive in the sealed cells or had matured 

 and left their shedding skins amid the dissected spiders. In 

 that case only were they considered true parasites, destroying 

 living matter. Yet we cannot prove that even here they had 

 destroyed living matter since they may have entered cells which 

 contained no egg or in which the larva was already dead. 



Of the 4,397 cells, 171 or 4 per cent, were in this condition, 

 i. e., the cell properly sealed and the contents destroyed by 

 this pest. 



Fifty cells gave forth Dipterous parasites, and 5 cells pro- 

 duced cuckoo bees; 54 cells contained the small house-renting 

 Trypoxylon clavatum, and 2 cells had been filled with cater- 

 pillars and resealed, evidently by an Eumenid wasp; one cell 

 contained an adult chick-beetle which was probably only using 

 the cell for shelter and 3 cells harbored larvae of the dark meal- 

 worm, Tenebico obscuris, and 1 cell contained a Lipidopterous 

 pupa which later gave forth an adult. 



Since the young wasps in the Melittobia infested cells had 

 completely spun their cocoons, it is quite likely that a large 

 per cent of them would have emerged as good adults, had not 

 the parasites killed them. In so far as building and provisioning 

 were concerned the mother wasp was not at fault in these, while 



